It is proposed to localize precisely the acetylcholine (ACh) known to be present in large concentrations in the corneal epithelium, utilizing the technique of dry emulsion autoradiography. Because of the high water solubility of ACh, its histological demonstration has proven difficult in the past. Use of dry emulsion, freeze-drying and Spurr resin based techniques had made it possible precisely to localize ACh in the rabbit retina, and I propose to adapt the technique to the corneal epithelium. Freshly excised rabbit corneas will be incubated in the presence of 3-H-choline and sectioned with attention to moisture-free technique after freeze-drying and embedding. One or two micron sections will then pressed onto dried emulsion slides and allowed to develop in the dark. A precise localization of ACh should be determined in this manner. Supporting evidence of ACh presence will be obtained by high voltage electrophoresis of supernatant obtained from homogenates of portions of the incubated tissue. Localization of ACh under control conditions will then be compared to levels and location following fifth cranial nerve sectioning and following epithelial wounding and during repair.